Extinguishing gas filtering device and electric current switchgear comprising such a filtering device

ABSTRACT

An extinguishing gas filtering device for an electric current switchgear with separable contacts, including an electric arc extinguishing chamber, includes, assembled together an inlet part for the extinguishing gases, made of a metal material and including an inlet aperture intended to be fluidically connected with an extinguishing gas outlet of the switchgear; an outlet aperture; a flared wall extending between the inlet and outlet apertures; a gas diffuser, which covers the outlet aperture, being planar in shape and including through-apertures; a filter made of porous metal foam, placed at the output of the gas diffuser.

The present invention relates to an extinguishing gas filtering devicefor an electric current switchgear. The invention also relates to anelectric current switchgear comprising such a filtering device.

Electrical units, such as circuit breakers or contactors, are known andmake it possible to selectively interrupt the flow of an electriccurrent within an electrical circuit, for example within an electricaldistribution network for domestic or industrial use.

This switchgear includes separable electrical contacts connected toinput and output terminals for an electric current. These electricalcontacts are selectively moveable between a closed position, in whichthey allow the electric current to flow between the terminals and,alternatively, an open position in which they are separated from oneanother so as to prevent this electric current from flowing.

It is known in particular that, when these electrical contacts are movedto their open position when an electric current is flowing therein, anelectric arc may form between these two electrical contacts. Thiselectric arc ionizes the ambient air in the switchgear, therebygenerating gases, termed extinguishing gases, that are then released tothe outside of the switchgear. The electric arc is then extinguished byway of an arc extinguishing chamber within the switchgear, so as tointerrupt the flow of the electric current.

The extinguishing gases exhibit a high temperature, typically greaterthan 4000° C., and comprise particles such as soot that generally stemfrom partial melting of various internal components of the switchgearunder the action of the electric arc.

The extinguishing gas therefore has to be cooled and deionized, by wayof a dedicated filtering device of the switchgear, before being releasedto the outside. This makes it possible in particular to avoid theelectric arc current looping back outside the switchgear, for examplebetween the input and/or output terminals and external metal parts, forexample within an electrical switchboard, on account of the highelectrical conductivity of the ionized extinguishing gas. Such loopingback leads to the formation of a short circuit, causing an unacceptableand dangerous safety breach.

There are filtering devices that aim to cool the extinguishing gasesbefore they leave. However, these known filtering devices do not make itpossible, in addition to reducing the temperature, to reduce thepressure of the extinguishing gases when they escape.

Now, the pressure increase generated during short circuits byswitchgear, in particular upon the interruption of currents exhibiting ahigh power, poses a safety problem in particular when this switchgear isinstalled in a confined area, such as an electrical enclosure or anelectrical panel. In this case, the excess pressure may seriously damagethe electrical switchgear and elements situated around it.

It is these drawbacks that the invention intends more particularly torectify, by proposing an extinguishing gas filtering device for anelectric current electrical switchgear with air switching, thisfiltering device making it possible, in a satisfactory manner, to reducethe temperature of the extinguishing gases generated by this electricalswitchgear while at the same time limiting the pressure of theextinguishing gases.

To this end, the invention relates to an extinguishing gas filteringdevice for an electric current switchgear with separable contacts andincluding an electric arc extinguishing chamber, this filtering deviceincluding, assembled together:

-   -   an inlet part for the extinguishing gases, this inlet part being        made of a metal material and including:        -   an inlet aperture intended to be fluidically connected with            an extinguishing gas outlet of an electric current            switchgear,        -   an outlet aperture, and        -   at least one flared wall extending between the inlet and            outlet apertures;    -   a gas diffuser, which covers the outlet aperture of the inlet        part, this gas diffuser being planar in shape and comprising        through-apertures;    -   a filter made of porous metal foam, placed at the output of the        gas diffuser.

By virtue of the invention, the use of an inlet part made of a metalmaterial with flared walls makes it possible to channel the jet ofextinguishing gas when it leaves the extinguishing chamber. On accountof the fact that the part is made of a metal material, and not ofplastic, the ablation of material caused by the jet of gas when itpasses into the inlet part generates less gas than in known filteringdevices made of plastic, thereby limiting the increase in the pressureof the extinguishing gases.

The diffuser makes it possible to distribute the entering extinguishinggas flow over the entire surface area of the filter, thereby increasingthe effectiveness of the filtering provided by the latter and preventingthe jet of gas from being concentrated locally, which could pierce thefilter. Lastly, as the filter is made of metal foam, it providessignificant cooling while at the same time occupying a low volume, onaccount of the high porosity of the metal foam.

Thus, the combination of the inlet part, the gas diffuser and the filtermakes it possible to cool the extinguishing gas by absorbing a largeamount of energy from the latter, while at the same time limiting thepressure increase, all with a compact architecture.

According to some advantageous but non-mandatory aspects of theinvention, such a filtering device may incorporate one or more of thefollowing features, either alone or in any technically permissiblecombination:

-   -   The inlet part includes an additional inlet aperture that is        intended to be connected fluidically to an output of an        extinguishing chamber, at least one of the walls of the inlet        part extending from this additional inlet aperture to the outlet        aperture.    -   The gas diffuser includes a membrane of wire cloth.    -   The wire cloth membrane is a weave cloth made of stainless steel        formed by weaving metal strands with a diameter greater than or        equal to 1 mm.    -   The gas diffuser includes an assembly of perforated metal        plates.    -   The metal foam of the filter has a porosity greater than or        equal to 90%.    -   The metal foam of the filter is made of nickel or of        nickel-chromium alloy.    -   The inlet part is made of stainless steel or of nickel-plated        steel.

According to another aspect, the invention relates to an electriccurrent switchgear, this switchgear comprising:

-   -   a cutoff block containing:        -   separable electrical contacts connected to input and output            terminals for an electric current and        -   an electric arc extinguishing chamber, for extinguishing an            electric arc formed upon the separation of the separable            electrical contacts, this extinguishing chamber being linked            fluidically to an extinguishing gas outlet of the            switchgear;    -   an extinguishing gas filtering device connected fluidically to        the extinguishing gas outlet;        the switchgear being characterized in that the filtering device        is in accordance with what is described above.

According to some advantageous but non-mandatory aspects of theinvention, such a switchgear may incorporate the following feature: thecutoff block includes a second extinguishing chamber comprising a secondextinguishing gas outlet, the switchgear comprising a second filteringdevice positioned at the output of the second outlet, the first andsecond filtering devices being identical to one another, the inletaperture of said filtering device being connected fluidically to saidextinguishing gas outlet, the additional inlet aperture of the secondfiltering device being connected fluidically to said secondextinguishing gas outlet.

The invention will be better understood and other advantages thereofwill become more clearly apparent in the light of the followingdescription of one embodiment of an extinguishing gas filtering devicegiven solely by way of example and with reference to the appendeddrawings, in which:

FIG. 1 is a schematic depiction, in a perspective view of a longitudinalsection, of an electric current switchgear including an extinguishinggas filtering device according to the invention;

FIG. 2 is a schematic depiction, in an external and perspective view, ofthe switchgear of FIG. 1;

FIG. 3 is a schematic depiction, in an exploded view, of anextinguishing gas filtering device of the switchgear of FIG. 1;

FIG. 4 is a schematic depiction of a housing of the switchgear of FIGS.1 and 2, comprising connection zones for receiving the extinguishing gasfiltering device of FIG. 3.

FIGS. 1 and 2 show a switchgear 2 for an electric current with separableelectrical contacts and with air switching.

In this example, the switchgear 2 is a low-voltage and high-currentmultipolar circuit breaker. For example, the switchgear 2 is designed tooperate with electric voltages lower than or equal to 1000 volts AC and1500 volts DC, and with electric currents having a short-circuitintensity of higher than or equal to 1 kA.

The switchgear 2 is in this case designed to act on a three-phasecurrent and, to this end, includes three separate poles, each associatedwith one phase of the electric current.

As a variant, the switchgear 2 may be different. It may be for example acontactor or a DC circuit breaker. The switchgear may also include adifferent number of poles, and for example be a unipolar or tetrapolarswitchgear.

The switchgear 2 is intended to be connected to an electrical circuit inorder to protect it against electrical faults, such as a short circuitor an overcurrent.

To this end, the switchgear 2 includes what are termed upstreamconnection terminals 4, 4′ and 4″, each associated with one phase of theelectric current. Likewise, the switchgear 2 includes what are termeddownstream connection terminals 6, 6′ and 6″. These upstream anddownstream connection terminals in this case extend in a mannerprojecting from a rear face 12 of a housing 8 of the switchgear 2, thisrear face 12 being opposite a front face 10 of the housing 8 of theswitchgear 2.

‘P1’ is used in this case to denote a longitudinal geometrical plane ofthe switchgear 2.

As illustrated in FIG. 1, the switchgear 2 includes a cutoff block 13,also called cutoff module, containing separable electrical contacts.These separable electrical contacts are in this case formed byassociating fixed electrical contacts 14, joined to a frame of theswitchgear 2, and mobile electrical contacts 16 that are moveable withrespect to the fixed contacts 14, between an open state and a closedstate. In FIG. 1, the contacts 14 and 16 are illustrated in the openstate.

In this example, the cutoff block 13 is associated with one of thephases of the current and is associated with the terminals 4 and 6.

The switchgear 2 in this case includes other cutoff blocks, eachassociated with one of the other electrical phases and each includingseparable electrical contacts. These cutoff blocks are preferably housedin separate compartments of the housing 8. The structure and thefunction of these cutoff blocks and of their separable contacts aresimilar to those of the cutoff block 13, such that the description givenhereinafter also applies thereto. For example, the switchgear 2 includestwo other cutoff blocks respectively associated with the two otherphases of the electric current and with the terminals 4′ and 6′, 4″ and6″.

In the closed state, the mobile contacts 16 are in electrical contactwith the fixed contacts 14 and thus allow an electric current to flowwithin the switchgear 2 between the opposite terminals 4 and 6. In theopen state, the mobile contacts 16 are spaced apart from the fixedcontacts 14 so as to prevent the flow of an electric current, thecontacts 14 and 16 thus being electrically isolated by the ambient air.The electric current is thus prevented from flowing between the oppositeterminals 4 and 6, at least when there is no electric arc present.

The fixed contacts 14 and the mobile contacts 16 in this case bearcontact tabs, respectively denoted 20 and 21 and in this case made ofcopper, that are intended to promote better electrical conductivitybetween the contacts 14 and 16 when they are in the closed state.

In the present case, there are two fixed contacts 14, one beingconnected electrically to the terminal 4 and the other being connectedto the terminal 6. The mobile contacts 16 are connected electrically toone another. In this case, there are two of them, each being associatedwith a fixed contact 14.

In this illustrative example, the mobile contacts 16 are formed by asingle part made of an electrically conductive material, which is borneby a rotary unit 22 mounted so as to rotate with respect to the housing8. The fixed contacts 14 are in this case positioned symmetrically aboutthe axis of rotation of the unit 22.

In a known manner, when two electrical contacts 14 and 16 separate whilean electric current is flowing through the switchgear 2, an electric arcoccurs between these contacts 14 and 16, for example between thecorresponding tabs 20 and 21. This electric arc stems from the breakagein isolation in the air between the contacts 14 and 16 and is maintainedby ionization of the ambient air. This results in an increase intemperature and in pressure, as the electric arc in turn brings aboutthe ionization of components of the switchgear 2, for example theionization of the contact tabs 20, 21 and/or of the walls of the housing8, thereby giving rise to an extinguishing gas. The electric arc is thusaccompanied by a sharp increase in temperature and in pressure insidethe switchgear 2.

By way of illustrative example, for a circuit breaker operating at avoltage of 690 V and a cutoff current equal to 100 kA, the energy of theelectric arc may reach up to 100 kJ. The extinguishing gas pressure mayreach up to 30 bar. In the absence of a filtering device, theextinguishing gas is released outside the housing 8 at a temperaturehigher than 4000° C. and a sonic speed greater than 300 m/s.

The switchgear 2 also includes arc extinguishing chambers 24 and 24′,the role of which is to extinguish such an electric arc. Eachextinguishing chamber 24, 24′ is thus, in this example, associated withand placed facing a zone of contact between a fixed contact 14 and amobile contact 16. For example, the extinguishing chamber 24 isassociated with the electrical contacts 14 and 16 that are on the sideof the upstream terminal 4, and the extinguishing chamber 24′ isassociated with the electrical contacts 14 and 16 that are on the sideof the downstream terminal 6.

The extinguishing chamber 24 includes a stack of sheets 26, also calledarc separation plates, and an extinguishing gas evacuation channel 30that opens out outside the housing 8 of the switchgear 2 at a gas escapeoutlet. The role of the plates of the stack 26 is to extinguish theelectric arc by splitting it into a plurality of separate arcs betweenthe plates. The role of the evacuation channel 30 is to evacuate theextinguishing gas out of the housing of the switchgear 2 towards thecorresponding gas outlet.

The evacuation channel 30 in this case includes a protective grating 32so as to prevent the entry of foreign bodies into the extinguishingchamber 24, for example so as to ensure sealtightness against dustand/or against foreign bodies with a diameter greater than 1 mm. Thisgrating 32 may be omitted, however.

In practice, the extinguishing gases coming from this extinguishingchamber 24 are in this case only able to escape out of the switchgear 2by way of the channel 30. For example, the housing 8 is made of agastight material.

As a variant, the cutoff block 13 may include a different number ofextinguishing chambers. The number of extinguishing chambers is in thiscase chosen depending on the number and on the position of the fixed 14and mobile 16 contacts forming these separable contacts. For example,the switchgear 2 may include just one extinguishing chamber when itincludes just one fixed contact 14 and one mobile contact 16 that areassociated with this electrical phase.

The extinguishing chambers 24 and 24′ are similar in this case. Inparticular, the extinguishing chamber 24′ in particular includes a stack26′ and an evacuation channel 30′ that are analogous to the stack 26 andto the evacuation channel 30, respectively. In this example, thechambers 24 and 24″ differ from one another in particular in terms oftheir position within the cutoff block and in terms of the spatialconfiguration of the channels 30 and 30′, as described hereinafter.

In this example, the channels 30 and 30′ open out outside the housing 8each by way of an outlet, such as one or more orifices or apertures,situated on a face, respectively upper and lower, of the housing 8.

The movement of the mobile electrical contacts 16 with respect to thefixed contacts 14 is ensured by way of a control mechanism 40, which isnot described in greater detail hereinafter. This control mechanism 40is in this case able to be actuated manually by an operator, by way of acontrol lever 42 situated on the front face 10 of the switchgear 2. Themechanism 40 is also able to be actuated automatically, for example inthe event of an electrical fault detected by way of a tripping device 44integrated into the switchgear 2. For example, the tripping device 44 isa thermal and/or magnetic trip.

In this example, the mechanism 40 is designed to control thesimultaneous movement of the mobile electrical contacts belonging to thevarious cutoff blocks of the switchgear 2.

The switchgear 2 also includes at least one filtering device 50 whoserole is to cool and decontaminate the extinguishing gases and to reducethe pressure thereof before they are evacuated out of the switchgear 2.

As illustrated in FIG. 3, the filtering device 50 includes an inlet part52, a gas diffuser 54 and a filter made of metal foam 56. In FIG. 3,these elements are illustrated in an exploded view so as to facilitateunderstanding. However, in practice, these elements are assembledtogether so as to form the filtering device 50. ‘X50’ is used to denotea longitudinal axis of the filtering device 50, and ‘P2’ is used todenote a transverse geometrical plane of the filtering device 50.

For example, the inlet part 52, the gas diffuser 54 and the filter 56are assembled and aligned with one another along the axis X50.

In this example, each cutoff block of the switchgear 2 includes twofiltering devices 50, each placed at the output of an extinguishingchamber 24, 24′ of this cutoff block, that is to say in this case at theoutlet of the corresponding evacuation channel 30, 30′, so as to collectand filter the extinguishing gases coming from this cutoff block. As avariant, when the cutoff blocks include a different number ofextinguishing gas outlet apertures, the number of filtering devices 50is changed as a result, so that each extinguishing gas outlet apertureis provided with a filtering device 50.

In FIG. 1, the two filtering devices 50 associated with the cutoff blockdescribed above bear the references 50 a and 50 b, respectively, so asto differentiate them in the following description. In this example, thefiltering device 50 a is placed at the outlet of the extinguishingchamber 24, and the filtering device 50 b is placed at the outlet of theextinguishing chamber 24′. More precisely, the devices 50 a and 50 b areplaced at the outlet of the evacuation channels 30 and 30′,respectively.

The inlet part 52 is in this case made of a metal material, preferablyof nickel-coated steel. The metal material may be different, however,and for example be stainless steel.

The inlet part 52 includes an inlet aperture 60, termed main aperture.This inlet aperture 60 is intended to be connected fluidically to anextinguishing gas outlet of the switchgear 2, preferably in a sealtightmanner, so as to allow extinguishing gases to pass from the gas outletto inside the filtering device 50.

‘Connected fluidically’ is understood to mean in this case that elementsare connected to one another so as to allow a fluid, such as a gas, toflow, preferably in a sealtight manner, that is to say limiting leakagesout of these elements at the points where they are connected.

The inlet part 52 also includes an outlet aperture 66. The inlet part 52also includes inlet walls 62, 64 that in this case extend from the inletaperture 60 to the outlet aperture 66.

The inlet aperture 60 has dimensions smaller than those of the outletaperture 66. For example, the surface area of the inlet aperture 60 doesnot exceed that of the extinguishing gas aperture with which it isassociated. By limiting the dimensions of the orifice, the risk of theelectric arc being able to escape out of the extinguishing chamber 24,24′ towards the filtering device 50 is reduced, thereby limiting therisk of the electric current looping back outside the switchgear 2.

The walls 62, 64 in this case have a flared form that widens from theinlet aperture 60 towards the outlet aperture 66.

In this example, the walls 62 and 64 partly define a first portion 68 ofthe part 52, this first portion 68 having a flared form, like a funnel,that in this case widens along the axis X50 and ends in a first orificewith a surface area greater than that of the inlet orifice 60. Thisfirst orifice is in this case positioned facing the outlet aperture 66and opens out into this outlet aperture 66. This first orifice in thiscase has dimensions smaller than those of the outlet aperture 66. Inthis case, the first portion 68 extends parallel to the axis X50. As avariant, the first portion 68 may have a different form, for example aconical form.

Furthermore, the inlet part 52 optionally includes a secondary inletaperture 70, also called additional inlet aperture. In the exampleillustrated, the additional aperture 70 is formed underneath the firstportion 68. The part 52 also includes an inclined wall 72 that extendsfrom the additional aperture 70 towards the outlet aperture 60.

The position and the dimensions of the inlet aperture 60 and, whereapplicable, of the additional aperture 70 are chosen depending on theform and on the location of the extinguishing gas escape outlets, asexplained hereinafter.

The flared form of the walls 62, 64, and therefore of the first portion68, and also the inclined form of the wall 72, play a part in deflectingand orienting the jet of extinguishing gas towards the gas diffuser 54when said jet penetrates into the inlet part 52.

The inlet part 52 also has a second portion, partly defined by walls 74,76 and by planar lateral walls that are not referenced. The secondportion is formed in the extension of the first portion 68. The lateralwalls in this case extend from the first portion and from the secondaryaperture 70 as far as to the outlet aperture 66.

In this example, on account of the design of the switchgear 2, theextinguishing chambers 24 and 24′ and the escape channels 30, 30′ arepositioned differently and asymmetrically. The evacuation channels 30,30′ therefore open out at different positions on opposite faces of thehousing 8. For example, the channel 30 opens out outside the housing 8at an escape outlet situated essentially in the middle of the upperface, and the channel 30′ opens out outside the housing 8 at an escapeoutlet situated at an edge of the lower face, in particular due to thepresence of the tripping device 44 that prevents it from opening out inthe middle of the lower face.

The additional inlet aperture 70 is in this case intended to beconnected fluidically to the output of the channel 30′, whereas theinlet aperture 60 is in this case intended to be connected fluidicallyto the output of the channel 30. In this case, the additional apertureof the filtering device 50 a opens out at a portion of the housing 8 anddoes not receive extinguishing gas. Analogously, the inlet aperture 60of the filtering device 50 b opens out at a wall of the housing 8 anddoes not receive extinguishing gas.

Thus, one and the same filtering device 50 model may be associated withgas outlets placed at different locations on the switchgear 2 that havedifferent orientations and/or geometries. It is therefore not necessary,within one and the same switchgear 2, to resort to filtering deviceshaving different geometries. This therefore simplifies manufacture ofthe switchgear 2 on an industrial scale, both in terms of cost and interms of managing the parts necessary for manufacture.

As a variant, the part 52 may be different. In particular, the secondaryinlet aperture 70 may be omitted. This is the case for example when thecutoff block of the switchgear 2 contains just one extinguishing chamber24. The number and the form of the walls 62, 64 may also be different.

According to other variants, filtering devices 50 a and 50 b that aredifferent from one another may be used within the switchgear 2, each forexample adjusted to the position and/or to the form of the extinguishinggas outlets. Here again, the secondary inlet aperture 70 may be omittedwhen the inlet part 52 is adjusted to the form and to the position ofthe extinguishing gas outlet.

The role of the diffuser 54 is to promote the distribution of the flowof extinguishing gas entering the part 52 over the entire inlet surfacearea of the filter 56, in particular so as to prevent the jet of gasfrom being concentrated completely on a precise zone of the filter 56,which could damage it.

Preferably, the diffuser 54 includes a layer, or membrane, of wire clothformed by weaving metal strands. These metal strands preferably have alarge thickness, for example have a diameter greater than 1 mm.Advantageously, the cloth has a ‘weave’-type mesh.

This layer of cloth has a planar form and in this case extends parallelto the plane P2 in the outlet aperture 66 over the entire surface areaof the cross section of the outlet aperture 66. Thus, the entering jetof gas has to pass through the diffuser 54 in order to reach the filter56. The woven-together wires thus define between them a plurality ofthrough-apertures that allow the extinguishing gas to pass through thewire cloth membrane by travelling therethrough. For example, the layerof cloth is stretched between the walls 74 and 76 of the inlet part 52.

Advantageously, the wire cloth is in this case made of stainless steel,preferably of ‘AISI 316L’ type, with weft strands having a diametergreater than or equal to 1.4 mm and warp strands having a diametergreater than or equal to 2 mm, preferably with a weave having a plainweave structure.

As a variant, the metal weave cloth may be produced differently, forexample with different strand diameters and/or a different weavestructure. The strands forming the cloth may be made of a stainlesssteel of ‘AISI 304L’ type.

According to another embodiment, the diffuser 54 includes an assembly ofmetal plates or sheets that are perforated with apertures. These platesare positioned in the outlet aperture 66 so as to cover the outletaperture 66. They perform a role analogous to the wire cloth describedabove. For example, these metal plates are positioned parallel to oneanother, in this case along the plane P2, and are spaced apart from oneanother along the axis X50. Preferably, the perforations are formed onthese plates so as to be positioned in a manner offset with respect tothe perforations of the immediately adjacent plates, that is to say thatthese perforations are not situated facing the perforations of theimmediately adjacent plates and are not aligned with these perforationsof the immediately adjacent plates. This prevents the jet ofextinguishing gas from passing through the diffuser 54 in a straightline and, by contrast, promotes the travel and the spatial distributionof the extinguishing gas through the diffuser 54.

The filter 56 includes a layer of porous metal foam, placed at theoutput of the gas diffuser 54, for example by being coupled to thelatter and covering an outlet face thereof over the entire surface areathereof. As a variant, the filter 56 includes a stack of a plurality ofsuch layers of metal foam that are coupled to one another. For example,the layer(s) of metal foam are positioned parallel to the plane P2between the walls 74 and 76 of the inlet part 52. Preferably, thelayer(s) of foam are assembled in a sealtight manner, in order toprevent the extinguishing gas coming from the diffuser 54 from beingable to escape out of the filtering device 50 without passing throughthe filter 56.

This metal foam has a high porosity, for example greater than or equalto 90% and, preferably, greater than or equal to 95%. Porosity isdefined in this case as being the ratio between the volume of the emptyspace contained inside a volume of foam, on the one hand, and saidvolume of foam, on the other hand.

The metal foam has a porous alveolar structure formed of a solid metalmaterial. In fact, it has a high exchange surface area, for examplegreater than or equal to 1500 m² per cubic metre of foam and,preferably, greater than or equal to 2500 m² per cubic metre or, evenmore preferably, greater than or equal to 2800 m² per cubic metre.

The pores of the metal foam open out outside the layer of foam, forexample at outer faces of this layer. Thus, the extinguishing gasesleaving the diffuser 54 are able to enter the layer 56 and passtherethrough so as then to emerge from it outside the filtering device50.

Preferably, the metal foam is made of nickel. As a variant, the foam 56may be made of a nickel-chromium alloy.

The combination of the inlet part 52, the gas diffuser 54 and the filter56 makes it possible to cool the extinguishing gas by absorbing a largeamount of energy from the latter, while at the same time limiting theablation of material by the extinguishing gas. Now, in known filteringdevices, the pressure increase that is typically observed is for themost part caused by the ablation of material by the hot extinguishinggas, particularly when these devices are made of plastic. By limitingthe ablation of material, the increase in the pressure that is typicallyobserved in known devices is limited. Even when such an ablation occurs,the pressure increase is not as great, as the metal materials that areused are not as gasogenic as the plastic materials of known devices,that is to say that they release less gas when they are exposed to thehot extinguishing gas flow.

By virtue of the invention, the extinguishing gases leaving thefiltering device 50 are cooled in a satisfactory manner, and thepressure thereof is lower in comparison with known filtering devices.For example, the inventors have determined that, in some cases, thepressure of the extinguishing gases is four times lower, or even fivetimes lower, than the pressure of the extinguishing gases at the outputof known filtering devices.

On account of the performance of the filtering device 50, the operationof the switchgear 2 is more secure. It is able to be used in a confinedenvironment while limiting the risk of damaging its environment when thecurrent is cut off.

In this embodiment, as illustrated in FIGS. 2 and 4, the filteringdevices 50 of the switchgear 2 are grouped within filtering assemblies80, which each group together a plurality of filtering devices 50associated with various cutoff blocks of the switchgear 2.

The extinguishing gas outlets of the switchgear 2 are in this casesituated on an upper face of the housing 8 in an upper zone 82, and on alower face of the housing 8 in a lower zone 84. The switchgear 2therefore includes two filtering assemblies 80, one associated with theoutputs placed in the zone 82 and fixed to the housing 8 in this zone82, and the other associated with the outputs placed in the zone 84 andfixed to the housing 8 in this zone 84.

The filtering assemblies 80 are in this case identical and each includethree filtering devices 50 that are preferably identical to one another.

As illustrated in FIG. 4, the lower zone 84 includes three recesses 86,or cavities, each formed at the base of the housing 8 in the alignmentof one of the cutoff blocks. The recesses 86 are separated from oneanother by separating walls 87 that are in this case vertical and extendperpendicularly to the lower face, in this case parallel to the planeP1. These separating walls 87 are in this case formed contiguously withthe housing 8.

Each of these recesses 86 also encloses a connection interface 88 forreceiving one end of a connection terminal 6, 6′, 6″. Each interface 88is in this case provided with a bore, which is for example tapped,intended to receive a fastening screw that holds the correspondingterminal 6, 6′, 6″ end. This interface 86 furthermore includes a plasticcasing on which the bore is formed and that surrounds an extension ofthe fixed contact 14. Thus, when the terminal 6, 6′, 6″ is received inthe corresponding interface 88, it is in electrical contact with thisextension of the fixed contact 14.

The zone 84 also includes apertures 90 that are linked to the channel30′ and that together form an outlet for the extinguishing gases comingfrom the extinguishing chamber 24′. The apertures 90 are in this caseplaced at a rear edge of the zone 84.

These apertures 90, and also the channel 30′ that extends as far asthese apertures 90, are separated from the bore formed on the interface86 and from the fixed contact 14 by electrically insulating internalwalls of the housing 8 that are sealtight with respect to theextinguishing gas. In this way, the extinguishing gases are able toleave the housing 8 through this outlet without otherwise coming intoelectrical contact with the connection terminals 6, 6′, 6″. A risk ofthe current looping back within the switchgear 2 is thus prevented.

The assembly 80 furthermore includes a separating part 92 that isassembled on the lower face in the zone 84. This part 92 includes inparticular separating walls 94 that extend the separating walls 87, thusdefining recesses in the extension of the recesses 86. The part 92 alsoincludes a cover 96, applied to its front face so as to mask and protectthe recesses 86.

A filtering device 50 is received in each of these recesses. The inletpart 52 of each of these filtering devices 50 is pressed flat againstthe base of the housing 8 in the zone 84 so as to be positioned suchthat the secondary inlet aperture 70 is placed facing the correspondingapertures 90.

The upper zone 82 is produced analogously, if only in this case, and theinterfaces 88 allow the connection of the terminals 4, 4′ and 4″.Furthermore, the evacuation channel 30 in this case has a geometrydifferent from that of the evacuation channel 30′ and opens out at alocation separate and remote from the interface 86. The part 52 of eachof the filtering devices 50 is pressed flat against the base of thehousing 8 in the zone 82 so as to be positioned such that the main inletaperture 60 is placed facing the outlet of the evacuation channel 30.The apertures 90 may then be omitted.

The embodiments and the variants contemplated above may be combined withone another so as to create new embodiments.

The invention claimed is:
 1. An extinguishing gas filtering device foran electric current switchgear with separable contacts and including anelectric arc extinguishing chamber, said extinguishing gas filteringdevice comprising: an inlet part for extinguishing gases, said inletpart being made of a metal material and including: an inlet aperturefluidically connected with an extinguishing gas outlet of the electriccurrent switchgear, an outlet aperture, and at least one flared wallextending between the inlet and outlet apertures; a gas diffuser, whichcovers the outlet aperture of the inlet part, said gas diffuser beingplanar in shape and including through-apertures; and a filter made ofporous metal foam and placed at an output of the gas diffuser.
 2. Thefiltering device according to claim 1, wherein the inlet part includesan additional inlet aperture that is intended to be connectedfluidically to an output of an extinguishing chamber, at least one ofthe walls of the inlet part extending from said additional inletaperture to the outlet aperture.
 3. The filtering device according toclaim 1, wherein the gas diffuser includes a membrane of wire cloth. 4.The filtering device according to claim 3, wherein the wire clothmembrane is a weave cloth made of stainless steel formed by weavingmetal strands with a diameter greater than or equal to 1 mm.
 5. Thefiltering device according to claim 1, wherein the gas diffuser includesan assembly of perforated metal plates.
 6. The filtering deviceaccording to claim 1, wherein the metal foam of the filter has aporosity greater than or equal to 90%.
 7. The filtering device accordingto claim 1, wherein the metal foam of the filter is made of nickel or ofnickel-chromium alloy.
 8. The filtering device according to claim 1,wherein the inlet part is made of stainless steel or of nickel-platedsteel.
 9. An electric current switchgear, said switchgear comprising: acutoff block containing: separable electrical contacts connected toinput and output terminals for an electric current, and an electric arcextinguishing chamber for extinguishing an electric arc and formed uponthe separation of the separable electrical contacts, said extinguishingchamber being linked fluidically to an extinguishing gas outlet of theswitchgear; an extinguishing gas filtering device connected fluidicallyto the extinguishing gas outlet, wherein the extinguishing gas filteringdevice includes: an inlet part for the extinguishing gases, said inletpart being made of a metal material and including: an inlet apertureintended to be fluidically connected with an extinguishing gas outlet ofan electric current switchgear, an outlet aperture, and at least oneflared wall extending between the inlet and outlet apertures; a gasdiffuser, which covers the outlet aperture of the inlet part, said gasdiffuser being planar in shape and comprising through-apertures; and afilter made of porous metal foam, placed at the output of the gasdiffuser.
 10. The switchgear according to claim 9, wherein the cutoffblock comprises a second extinguishing chamber comprising a secondextinguishing gas outlet, the switchgear comprising a second filteringdevice positioned at an output of a second outlet, extinguishing gasfiltering device and the second filtering device being identical to oneanother, the inlet aperture of said second filtering device beingconnected fluidically to said extinguishing gas outlet, the additionalinlet aperture of the second filtering device being connectedfluidically to said second extinguishing gas outlet.